1. Field of the Invention
The present invention relates to an image forming method and apparatus, and an image recording apparatus using the principle of the image forming method and apparatus. In detail, the present invention relates to an image forming method and apparatus using the characteristics of the wettability change by heating, and an image recording and indicating apparatus using the principle of the image forming method and apparatus.
2. Description of the Related Art
As a new recording process, an image recording method using the characteristics of the wettability change by heating has been known (for example, Japanese Laid-Open Patent Application No. 3-178478). Such an image recording method uses the property that the receding contact angle of the top surface of a base material, which has poly-fluoroalkyl-acrylates applied thereto, increases when the base material is heated in air, and the receding contact angle of the top surface of the base material decreases when the base material is heated in liquid.
FIG. 1 illustrates an outline of a latent image forming method using the above-described characteristics of the wettability change by heating. In this latent image forming method, as shown in FIG. 1, a recording body 110 includes a base material 111 and a recording material 112 coated on the top surface of the base material 111. The recording material is formed of a material (the material having the characteristics of the wettability change by heating). The receding contact angle of this material changes in accordance with a heating temperature when the material is heated in a condition where the material is in contact with liquid, a solid, or a solid which becomes liquid when heated. A contact liquid (contact member) 113 is caused to come into contact with the top surface of the recording body 110, the top surface being the surface on which the above-mentioned recording material 112 has been coated. Then, the thus-coated surface of the recording body 110 is selectively heated by heating means (not shown in FIG. 1). Thus, a latent image is formed on the recording material 112, and this latent image is developed using a developer such as ink.
FIG. 2 shows a method of forming a latent image on the recording material proposed in Japanese Laid-Open Patent Application No. 3-178478. As shown in FIG. 2, in a condition where the outer surface of the recording body 110 is in contact with the contact member 113, using a heating device 114 such as a thermal head, the outer surface of the recording body 110 is selectively heated. Then, the recording body 110 is cooled in a condition in which the contact member 113 is in contact with the outer surface of the recording body 110. Thereby, a condition where only the portions which have been selectively heated get wet (hereinafter, referred to as a liquid attraction state) is formed. Thus, a latent image is formed. This latent image is developed by a developing means 115 and is transferred to a recording paper sheet 120 by a transfer means 116. The recording body 110 is rotated in the direction of the arrow, is cleaned by a cleaning roller 117, the image is cleared by a image removing heater 118, and, then, subsequent recording is performed as described above. Thus, in the recording method in the related art, in latent image formation, it is necessary to heat the recording body in the condition in which liquid, a solid which becomes liquid by steam or heating, or a solid which generates liquid or steam (hereinafter, referred to as a contact member) is in contact with the surface of the recording body. Further, it is also necessary to cool the recording body in the condition where the contact member is in contact with the surface of the recording body.
The arrangement that the surface of the recording body and the heating device are directly in contact with one another consumes little heat energy, and also, the sharpness of an image is high. However, a very fine contact heating device such as a thermal head includes electronic components and electric wiring. Accordingly, durability of the head against liquid is not high, and therefore, the device may be damaged. Further, it is necessary to supply the contact member, such as liquid, in the contact surface between the heating device and the surface of the recording body. A supply mechanism for this purpose is complicated. In order to solve these problems, the inventors of the present invention proposed that heating be performed from the rear side of the recording body in Japanese Laid-Open Patent Application No. 6-286299.
However, even in the proposed method, there are problems that the thickness of the recording body is limited, recording energy increases, and image degradation due to thermal diffusion occurs during heat conduction from the rear side to the front side of the recording body. Further, considering non-contact heating arrangements such as that using laser and so forth, the layer holding the contact member on the recording body needs to transmit light. Accordingly, a mechanism therefor is complicated. Thus, when selective heating is performed based on image information in the condition where the contact member such as liquid is in contact with the recording body, there are problems that the heating device is damaged due to the contact member or a mechanism for supplying the contact member is complicated.
In the above-described related art, the recording body is selectively heated while the contact liquid is being supplied when a latent image is formed. Even when any heating method is used, it is difficult to provide a stable supply of the contact liquid.